Immediately apply the updates released by software companies.
Be especially vigilant with updates of operating systems (such as Windows) and the applications that allow you to communicate through the Internet (browsers, e-mail clients or chat clients). With Microsoft products, it is advisable to regularly use the Windows Update tool in order to automate the process.

Use a good antivirus application and update it regularly.
Several aspects must be taken into account when choosing an effective antivirus, including its capacity to be updated (preferably daily) and customer services, which must be able to solve any type of incident in the shortest possible time. Similarly, a good antivirus will be certified by one of the leading industry watchdogs.

Make regular backup copies to safeguard important information.
If you do not have a specific device for backing up documents and files, you can copy them to floppy disk. In this case, a compression tool will be very useful for compressing the information in ZIP format or similar. Another option, which is becoming more readily available, is to use a recordable CD-ROM.

Create a boot disk and keep it in a safe place.
If you have problems starting your computer, a boot disk is very useful. It can also help disinfect boot viruses that have managed to get into your system and which require the computer to be booted from a clean boot disk.

Set secure, long passwords which contain words that cannot be found in a dictionary.
When choosing a password, it is a good idea to use the first letter of each word in a well-known proverb that you easily remember. For example, a password that may seem difficult to remember: 'echasl', could correspond to the proverb: "Every cloud has a silver lining".

Avoid using files with potentially dangerous formats.
It is advisable not to open or download -from websites- attached files with an .EXE extension. When sending text via e-mail, it is better to use ASCII files (created with notepad, for example), in order to block the entry of macro viruses that could hide in Word documents. If you need to send a text with certain specifications (different letter sizes, fonts, colors etc.) you can save them with an 'RTF' extension in order to avoid possible infection.

Use secure Web servers for transactions and sending confidential information.
You can find out if a Web server uses encryption in communications by looking at the URL address. The URL of a secure website start with https://. In addition, when you are browsing a secure website, the browser will display a closed lock icon on the status bar at the bottom of the window.

Reject files sent from unknown sources or unsolicited files.
One of the techniques mostly frequently used by attackers involves tricking victims into installing a Trojan by making them believe that the file they've received is a software tool or a photograph. Similarly, an attacker could ask victims to send them a system file needed to repair a computer. However, the file requested is actually used to store confidential information such as the mailbox password.

Configure the security options included in different applications to suit your needs and obtain the level of protection required.
In Internet Explorer, for example, you can set different security levels for each zone you browse. For Internet, it is advisable to set an intermediate to high level.

Consider installing an Uninterruptable Power Supply (UPS).
These systems prevent data loss if the power supply fails and protect the computer from problems which arise from power surges and fluctuations.